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Six Major Regions of the Brain (8-7) 1. The cerebrum 2. The diencephalon 3. The midbrain 4. The pons 5. The medulla oblongata 6. The cerebellum © 2013 Pearson Education, Inc. Major Structures of the Brain (8-7) • The cerebrum • Is divided into paired cerebral hemispheres • Deep to the cerebrum is the diencephalon • Which is divided into the thalamus, the hypothalamus, and the epithalamus • The brain stem • Contains the midbrain, pons, and medulla oblongata • The cerebellum • Is the most inferior/posterior part © 2013 Pearson Education, Inc. Figure 8-16a The Brain. Right cerebral hemisphere CEREBRUM Left cerebral hemisphere Longitudinal fissure A N T E R I O R Cerebral veins and arteries below arachnoid mater © 2013 Pearson Education, Inc. CEREBELLUM Superior view P O S T E R I O R Figure 8-16b The Brain. Central sulcus Precentral gyrus Postcentral gyrus Parietal lobe Frontal lobe of left cerebral hemisphere Lateral sulcus Occipital lobe Temporal lobe CEREBELLUM PONS Lateral view © 2013 Pearson Education, Inc. MEDULLA OBLONGATA Figure 8-16c The Brain. Corpus Precentral Central sulcus callosum gyrus Postcentral gyrus Fornix Frontal lobe Thalamus Hypothalamus DIENCEPHALON Pineal gland (part of epithalamus) Parieto-occipital sulcus Optic chiasm Mamillary body Temporal lobe MIDBRAIN Brain stem PONS MEDULLA OBLONGATA © 2013 Pearson Education, Inc. CEREBELLUM Sagittal section The Ventricles of the Brain (8-7) • Filled with cerebrospinal fluid and lined with ependymal cells • The two lateral ventricles within each cerebral hemisphere drain through the: • Interventricular foramen into the: • Third ventricle in the diencephalon, which drains through the cerebral aqueduct into the: • Fourth ventricle, which drains into the central canal © 2013 Pearson Education, Inc. Figure 8-17 The Ventricles of the Brain. Cerebral hemispheres Ventricles of the Brain Cerebral hemispheres Lateral ventricles Interventricular foramen Third ventricle Cerebral aqueduct Pons Medulla oblongata Spinal cord Fourth ventricle Central canal A lateral view of the ventricles © 2013 Pearson Education, Inc. Central canal Cerebellum An anterior view of the ventricles Cerebrospinal Fluid (8-7) • CSF • Surrounds and bathes the exposed surfaces of the CNS • Floats the brain • Transports nutrients, chemicals, and wastes • Is produced by the choroid plexus • Continually secreted and replaced three times per day • Circulation from the fourth ventricle into the subarachnoid space into the dural sinuses © 2013 Pearson Education, Inc. Figure 8-18a The Formation and Circulation of Cerebrospinal Fluid. Extension of choroid plexus into lateral ventricle Choroid plexus of third ventricle Cerebral aqueduct Lateral aperture Choroid plexus of fourth ventricle Median aperture Arachnoid mater Subarachnoid space Dura mater © 2013 Pearson Education, Inc. A sagittal section of the CNS. Cerebrospinal fluid, formed in the choroid plexus, circulates along the routes indicated by the red arrows. Arachnoid granulations Superior sagittal sinus Central canal Spinal cord The Cerebrum (8-7) • Contains an outer gray matter called the cerebral cortex • Deep gray matter in the cerebral nuclei and white matter of myelinated axons beneath the cortex and around the nuclei • The surface of the cerebrum • Folds into gyri • Separated by depressions called sulci © 2013 Pearson Education, Inc. The Cerebral Hemispheres (8-7) • Are separated by the longitudinal fissure • The central sulcus • Extends laterally from the longitudinal fissure • The frontal lobe • Is anterior to the central sulcus • Is bordered inferiorly by the lateral sulcus © 2013 Pearson Education, Inc. The Cerebral Hemispheres (8-7) • The temporal lobe • Inferior to the lateral sulcus • Overlaps the insula • The parietal lobe • Extends between the central sulcus and the parietooccipital sulcus © 2013 Pearson Education, Inc. The Cerebral Hemispheres (8-7) • The occipital lobe • Located most posteriorly • The lobes are named for the cranial bone above it • Each lobe has sensory regions and motor regions • Each hemisphere sends and receives information from the opposite side of the body © 2013 Pearson Education, Inc. Motor and Sensory Areas of the Cortex (8-7) • Are divided by the central sulcus • The precentral gyrus of the frontal lobe • Contains the primary motor cortex • The postcentral gyrus of the parietal lobe • Contains the primary sensory cortex © 2013 Pearson Education, Inc. Motor and Sensory Areas of Cortex (8-7) • The visual cortex is in the occipital lobe • The gustatory, auditory, and olfactory cortexes are in the temporal lobe © 2013 Pearson Education, Inc. Association Areas (8-7) • Interpret incoming information • Coordinate a motor response, integrating the sensory and motor cortexes • The somatic sensory association area • Helps to recognize touch • The somatic motor association area • Is responsible for coordinating movement © 2013 Pearson Education, Inc. Figure 8-19 The Surface of the Cerebral Hemispheres. Primary motor cortex (precentral gyrus) Central sulcus Primary sensory cortex (postcentral gyrus) Somatic motor association area (premotor cortex) PARIETAL LOBE Somatic sensory association area FRONTAL LOBE Visual association area OCCIPITAL LOBE Visual cortex Auditory association area Prefrontal cortex Gustatory cortex Insula Lateral sulcus Auditory cortex Olfactory cortex TEMPORAL LOBE © 2013 Pearson Education, Inc. Cortical Connections (8-7) • Regions of the cortex are linked by the deeper white matter • The left and right hemispheres are linked across the corpus callosum • Other axons link the cortex with: • The diencephalon, brain stem, cerebellum, and spinal cord © 2013 Pearson Education, Inc. Higher-Order Centers (8-7) • Integrative areas, usually only in the left hemisphere • The general interpretive area or Wernicke's area • Integrates sensory information to form visual and auditory memory • The speech center or Broca's area • Regulates breathing and vocalization, the motor skills needed for speaking © 2013 Pearson Education, Inc. The Prefrontal Cortex (8-7) • In the frontal lobe • Coordinates information from the entire cortex • Skills such as: • Predicting time lines • Making judgments • Feelings such as: • Frustration, tension, and anxiety © 2013 Pearson Education, Inc. Hemispheric Lateralization (8-7) • The concept that different brain functions can and do occur on one side of the brain • The left hemisphere tends to be involved in language skills, analytical tasks, and logic • The right hemisphere tends to be involved in analyzing sensory input and relating it to the body, as well as analyzing emotional content © 2013 Pearson Education, Inc. Figure 8-20 Hemispheric Lateralization. RIGHT HAND LEFT HAND Prefrontal cortex Prefrontal cortex Speech center Anterior commissure C O R P U S C A L L O S U M Writing Auditory cortex (right ear) General interpretive center (language and mathematical calculation) Analysis by touch Auditory cortex (left ear) Spatial visualization and analysis Visual cortex (right visual field) Visual cortex (left visual field) LEFT HEMISPHERE © 2013 Pearson Education, Inc. RIGHT HEMISPHERE The Electroencephalogram (8-7) • EEG • A printed record of brain wave activity • Can be interpreted to diagnose brain disorders • More modern techniques • Brain imaging, using the PET scan and MRIs, has allowed extensive "mapping" of the brain's functional areas © 2013 Pearson Education, Inc. Figure 8-21 Brain Waves. Patient being wired for EEG monitoring Alpha waves are characteristic of normal resting adults Beta waves typically accompany intense concentration Theta waves are seen in children and in frustrated adults Delta waves occur in deep sleep and in certain pathological conditions 0 Seconds 1 © 2013 Pearson Education, Inc. 2 3 4 Memory (8-7) • Fact memory • The recall of bits of information • Skill memory • Learned motor skill that can become incorporated into unconscious memory • Short-term memory • Doesn't last long unless rehearsed • Converting into long-term memory through memory consolidation • Long-term memory • Remains for long periods, sometimes an entire lifetime • Amnesia • Memory loss as a result of disease or trauma © 2013 Pearson Education, Inc. The Basal Ganglia (nuclei) (8-7) • Masses of gray matter • Basal nuclei • Subconscious control of skeletal muscle tone © 2013 Pearson Education, Inc. Figure 8-22 The Basal Nuclei. Head of caudate nucleus Lentiform nucleus Thalamus Tail of caudate nucleus Amygdaloid body Head of caudate nucleus Lateral view of a transparent brain, showing the relative positions of the basal nuclei Corpus callosum Lateral ventricle Insula Amygdaloid Lentiform Putamen nucleus Globus pallidus body Frontal section © 2013 Pearson Education, Inc. Tip of lateral ventricle The Limbic System (8-7) • Includes the olfactory cortex, basal nuclei, gyri, and tracts between the cerebrum and diencephalon • A functional grouping, rather than an anatomical one • Establishes the emotional states • Links the conscious with the unconscious • Aids in long-term memory with help of the hippocampus © 2013 Pearson Education, Inc. Figure 8-23 The Limbic System. Cingulate gyrus Corpus callosum Thalamic nuclei Hypothalamic nuclei Olfactory tract Amygdaloid body Hippocampus © 2013 Pearson Education, Inc. Fornix Mamillary body The Diencephalon (8-7) • Contains switching and relay centers • Centers integrate conscious and unconscious sensory information and motor commands • Surround third ventricle • Three components 1. Epithalamus 2. Thalamus 3. Hypothalamus © 2013 Pearson Education, Inc. The Epithalamus (8-7) • Lies superior to the third ventricle and forms the roof of the diencephalon • The anterior part contains choroid plexus • The posterior part contains the pineal gland that is endocrine and secretes melatonin © 2013 Pearson Education, Inc. The Thalamus (8-7) • The left and right thalamus are separated by the third ventricle • The final relay point for sensory information • Only a small part of this input is sent on to the primary sensory cortex © 2013 Pearson Education, Inc. The Hypothalamus (8-7) • Lies inferior to the third ventricle • The subconscious control of skeletal muscle contractions is associated with strong emotion • Adjusts the pons and medulla functions • Coordinates the nervous and endocrine systems © 2013 Pearson Education, Inc. The Hypothalamus (8-7) • Secretes hormones • Produces sensations of thirst and hunger • Coordinates voluntary and ANS function • Regulates body temperature • Coordinates daily cycles © 2013 Pearson Education, Inc. The Midbrain (8-7) • Contains various nuclei • Two pairs involved in visual and auditory processing, the colliculi • Contains motor nuclei for cranial nerves III and IV • Reticular formation is a network of nuclei related to the state of wakefulness • The substantia nigra influence muscle tone © 2013 Pearson Education, Inc. The Pons (8-7) • Links the cerebellum with the midbrain, diencephalon, cerebrum, and spinal cord • Contains sensory and motor nuclei for cranial nerves V, VI, VII, and VIII • Other nuclei influence rate and depth of respiration © 2013 Pearson Education, Inc. The Cerebellum (8-7) • An automatic processing center • Which adjusts postural muscles to maintain balance • Programs and fine-tunes movements • Ataxia • Is disturbance of coordination • Can be caused by damage to the cerebellum © 2013 Pearson Education, Inc. The Medulla Oblongata (8-7) • Connects the brain with the spinal cord • Contains sensory and motor nuclei for cranial nerves VIII, IX, X, XI, and XII • Contains reflex centers • Cardiovascular centers • Adjust heart rate and arteriolar diameter • Respiratory rhythmicity centers • Regulate respiratory rate © 2013 Pearson Education, Inc. Figure 8-24a The Diencephalon and Brain Stem. Cerebral peduncle Optic tract Cranial nerves N II N III N IV Thalamus Diencephalon Thalamic nuclei Midbrain Superior colliculus Inferior colliculus NV N VI Pons N VII N VIII N IX NX N XI N XII Spinal nerve C1 Spinal nerve C2 © 2013 Pearson Education, Inc. Cerebellar peduncles Medulla oblongata Spinal cord Lateral view Figure 8-24b The Diencephalon and Brain Stem. N IV Choroid plexus Thalamus Third ventricle Pineal gland Corpora quadrigemina Superior colliculi Inferior colliculi Cerebral peduncle Cerebellar peduncles Choroid plexus in roof of fourth ventricle Dorsal roots of spinal nerves C1 and C2 Posterior view © 2013 Pearson Education, Inc. Checkpoint (8-7) 20. Describe one major function of each of the six regions of the brain. 21. The pituitary gland links the nervous and endocrine systems. To which portion of the diencephalon is it attached? 22. How would decreased diffusion across the arachnoid granulations affect the volume of cerebrospinal fluid in the ventricles? 23. Mary suffers a head injury that damages her primary motor cortex. Where is this area located? © 2013 Pearson Education, Inc. Checkpoint (8-7) 24. What senses would be affected by damage to the temporal lobes of the cerebrum? 25. The thalamus acts as a relay point for all but what type of sensory information? 26. Changes in body temperature stimulate which area of the diencephalon? 27. The medulla oblongata is one of the smallest sections of the brain. Why can damage to it cause death, whereas similar damage in the cerebrum might go unnoticed? © 2013 Pearson Education, Inc. Reflexes (8-9) • Rapid, automatic, unlearned motor response to a stimulus • Usually removes or opposes the original stimulus • Monosynaptic reflexes • For example, the stretch reflex • Which responds to muscle spindles, is the simplest with only one synapse • The best known stretch reflex is probably the knee jerk reflex © 2013 Pearson Education, Inc. Simple Reflexes (8-9) • Are wired in a reflex arc • A stimulus activates a sensory receptor • An action potential travels down an afferent neuron • Information processing occurs with the interneuron • An action potential travels down an efferent neuron • The effector organ responds © 2013 Pearson Education, Inc. Figure 8-28 The Components of a Reflex Arc. Arrival of stimulus and activation of receptor Stimulus Activation of a sensory neuron Receptor Dorsal root Sensation relayed to the brain by axon collaterals Information processing in the CNS REFLEX ARC Effector Response by effector Ventral root Activation of a motor neuron © 2013 Pearson Education, Inc. KEY Sensory neuron (stimulated) Excitatory interneuron Motor neuron (stimulated) Figure 8-29 A Stretch Reflex. Stretching of muscle tendon stimulates muscle spindles Stretch Muscle spindle (stretch receptor) REFLEX ARC Spinal Cord Contraction Activation of motor neuron produces reflex muscle contraction © 2013 Pearson Education, Inc. Aging and the Nervous System (8-12) • Common changes • Reduction in brain size and weight and reduction in number of neurons • Reduction in blood flow to the brain • Change in synaptic organization of the brain • Increase in intracellular deposits and extracellular plaques • Senility can be a result of all these changes © 2013 Pearson Education, Inc. Checkpoint (8-12) 42. What is the major cause of age-related shrinkage of the brain? © 2013 Pearson Education, Inc.